Measurements of Two-Dimensional Strain Distribution Using the Electronic Speckle Pattern Interferometry.

Abstract

Electronic speckle pattern interferometry (ESPI) is a very useful method for measuring in-plane surface displacement. Using the cw-laser and image-processing system, it is possible to measure displacement and strain. Unlike traditional strain gauges or the moire method, the ESPI method requires no special surface preparation or attachments and can measure in-plane displacement with no contact and in real time. In this experiment, a specimen was loaded in parallel with a load cell, which provided loading step. The specimen was a flat plate or a plate with a 12 mm-diameter hole in its center. Strain gauges were attached to the specimen in x and y directions. This study provides an example of how ESPI has been used to measure two-dimensional displacement and strain distribution in this specimen. The results measured by ESPI are comparable with the data which were obtained by the strain-gauge method in tensile testing in the 1-ton range